Isothermal catalytic reforming



Feb. 16, 1960 M. w. MAYER v ISOTHERMAL CATALYTIC REFORMING Filed April 1, 1955 INVENTOR BY g -Q- ATTORNEY MAURICE W. MAYER r 2,925,311 ISOTHERMAL CATALYTIC REFORMING Maurice W; Ma er, Su'minmNJ,n signortejEsseRea search and Engineering Company, afoot-par tion f -Delaware a A v A pl cation April 1,, 1955, serial teaser "sciaims, (chzo'srls's) I the most serious problem, is the 'matter of,'supplying heatto the hydroforming. reaction to support the same. As the hydroforming process is conducted in conventional fixed .bed. operations, the naphtha to be ammedis preheated in a tubular furnace, admixed, with ahyd'ro- ,gen containin'g recyclefga's also heated in aitubular furnace, and the mixture is charged, to the first olf aqseiies of adiabatic reaction vessels each containing afixe'df bed of a suitable catalyst. The efiluentfrom thefir'streactor 'is' then passed through a reheat furnacewherelsufiicien't heat is supplied to compensate forlthe ,heatflossfoe casioned .by the endothermic reactionthat; has it-al en place in the first reactor vessel, so that: the temperature is restored to or near the temperature levelat which lit entered the first reactor. The reheatedmixtu're 'iis then passed intoa second reactionvessel and, if necessary, the efliuent therefrom is passed into a second .I reheat furnace and thence into ,a third vessel, and so on. The number ofreheatstages mightvary from one to tour depending upon the typeand severity of processing reduired. This arrangement is expensive in that it involves the use of many separate furnaces and vessels with concomitant valves, steam lines, purge systems, safety valves, .etc. and is particularly vur ldesirable for units of smallcap'acity'. H U l L As previously indicated, the present invention involves.

improvements in the :reforming of naphthas ,catalytically and substantially. isothermically for quality improvement ti include the production of hydrogen which is available for use in other processes, such as hydrodesulfurization, .by the use of a tubular reactor contained finafurnacev gaengnerre preheat the c ha rge stock anc lthe recycled ydfgfi, as well as to supply the heat of reaction.

While basically, the isothermal hydroforming process is old, thenovelty of the. present invention resides .in the particular range "ent ro'f equipment which will'allow mixed catalyst eperatiefi,e. treatment with platinumcontainingcatalysfdiifiiigthe first stage followed with a treatmeiit' lISi.fig. a'"filljilidfiiifii fifiiaifiing; ca alyst 01" vice versa, control 16f heatdinpu't to the different sectors of s lcha heater-reactor, [rise of tubes withou catalyst for heat inputeontfdl purposes, and the appli V on of the eyer aill technique outlined tor the manufacture of "hydrogen the main product from the naphtha' feed. I-n many -refineries'there e *h agen" require nts For example, many hydroc""b6ri contain substantial I quantities of sulfuig-and if these oils are to be processed. in a catalytic operation, the sulfur deactivatesthegcate.

alyst in a relatively shortperiodof time. Consequently," in dealing with sulfur-bearing stocks which are to-be treated catalytically in subsequentoperations; the said feedstock is subjected we mild hydrogenation to'convert the sulfur in thefeed stock to volatile sulfui'acom pounds,-such -as;HS. As is known, the hydroforming process invariablyresults in ainet production of hydro? 10 gen Moverand above that required forthehydroforming operation itself, andythis excess hydrogen maybe used to hydrodesulfurize' hydrocarbon 'oilsa The package's type equipmentfor the above purpdseswoul d reliable-the I construction of very jsmall size units at low 'cost;;-- i

.15 ..In brief-compass, the present invention involves the use of -a "system comprising, a singlefurnace containing,

the necessary heating, reaction, and reheating steps, with the=hydrocarbons and. hydrogen flowing through" heated nwtubes, which not; only eliminates. the added expense of the multiple pieces of equipment, but also permits opera= tion at, essentially isothermal conditions, which 'latter type of operationreduces the quantity of catalyst' re qnired-in the process andleifects animprovement in 'g'aso= -linefyields vas well, ,due to the fact 'that thenaphtha'i's not'preheated to thermal cracking conditions. A furth'er sess ;a longer =use'fulzlife due tothe fact that the proces's is carriedtout'under substantially uniform temperature conditions with noportion of'the catal'yst being heated 'above the average temperatureflevel required for good 1 operation; i, r I I In-cornp'aring the-present invention with prior practice, itis pointed out that in the{'conventionaboperation, naphtha is pumped into a hydroforming urlit'=at a pres- ;3 sure] of, say,,abont 540 p.s.i.g. and at a temperature of about 105 F., and then mixed "with hydrogen recycle ture is increased to about 965 This mixture at about 960 ':F. and a pressure of 5.17 -p.s.i.g. is'then passed over the first fixed bed of catalyst (say, a platinum-alumina catalyst) where the hydroforming reaction-occurs; and thiemperature falls rapidly in this first stageso that the mixture of naphtha and recycle gas passes from the Y first stage at a temperature-of about 843 :Th'is effiuentastream fisthen passed throughla furnace coil-or other heating means where it is reheated to ate'mpera'; ture of about965" F., and thereafter passedgthro'ilgh anothercatalyst-containing adiabatic;reactor fiom 'which his withdrawn at a temperature of about 7859, F, This reactor effiuent then passed through heat exchange equipment previously mentioned and cooling equipment, 'and finally into agaslseparator system where-the'recycle gas is separated froin the reformedan-aphtha product.- A

' portion of the gas is recycled through the system andi tjhe excess as, is bled off to a" gas collection means.- ,The W'naphtha product is-delivered t6 conventional stabilize. tron and fractio ation in a product recoverysysttiii. In the process embodying" the present inventio'ii, the anxiliai-y'steps of the conventional process, siic s separation, heat exchange, product and gas cooling'stabilization, fractionatiom'ete ,are the same as'in th conventional system, but the present improvements are in the furnace-tubular reactor system. The combined naphtha and-recycle gas is passed through the cenve 1 tional heat exchange equipmentain heat exchange with hotproduct, and is withdrawn therefrorii" at: a temper ature of about 720 F. and enters the reactor tubes of result of thepresent prdcess is that the'cataly s'twill 1505- gas atabout the same pressure level butat 'a slightly.

the combination furnace-tubular reactor. After preheating to a temperature of 920-930 F., thereby avoiding thermal cracking as would occur in' the'conventional system, the mixture is forced through tubes located in the furnace and acquires additional heat by firing heaters located in the reactor. The reaction continues under substantially isothermal conditions at about 920 F. until completed, and the eflluent from the furnace-reactor is delivered to the heat exchange equipment and the other steps previously outlined.

A modification of the present invention involves utilization of alternate banks of tubes containing no catalyst with banks of tubes containing catalyst in order to avoid excessive rates of heat input to the tubes containing catalyst. The naphtha in this modification is reheated in the tubes containing no catalyst. This modification would beparticularly desirable where highly naphthenic feeds were beingprocesse'd over very active catalyst, such as a platinum-containing catalyst, at high space velocities due,'of course, to the fact that the dehydrogenation of the naphthenes to the corresponding aromatics is a highly endothermic reaction. Also following treatment of the naphtha in the presence of a platinum-containing catalyst, the naphtha may be treated in tubes containing a molybdenum catalyst.

A further modification of the present invention involves passing the naphtha and recycle gas mixture through the catalyst-containing tubes in parallel banks to avoid high pressure drops and reduce compression and pumping expense.

A suitable method for arranging the tubes in a single piece of heater equipment would be to dispose them in a cylindrical case around the inner surface of the wall of said case, the said tubes extending in a vertical direction. A centrally disposed refractory baffle arrangement provides means for dividing the interior of the case into a plurality of sectors or zones and also provides means for' maintaining the various sectors at difierent temperature levels by manipulation of the heat-supplying means which latter may be individual burners disposed at a lower point in the said sectors or zones.

Among the objects'of the present invention are the following:

(1) The present invention provides a cheaper unit for processing hydrocarbons and finds particular useful application in relatively small scale operations.

(2) The process provides means for preventing thermal degradation of feed stocks by avoiding overheating of the feed stock in preheat furnaces, or the like, and this further results in:

(a) A longer catalyst useful life when the operation is catalytic.

(b) Increased yields of desired product.

(3) The present improvements require less and cheaper 7 equipment.

(4) The present improvements are adapted for use in hydroforming of high sulfur feed stocks to produce excess hydrogen suitable for use in other processes requiring hydrogen.

(5) The present process is adapted for mass production techniques for use in low capacity installations.

In accordance with the present invention, therefore, means are provided for providing a relatively small scale hydroforming plant which may be operated under conditions approaching isothermal operation, may be operated without preheating the naphtha to thermal cracking temperatures and otherwise avoiding the insufficiencies of the larger plants. v In the accompanying drawings, Fig. 1 represents an elevation partly in section of a furnace-tubular reactor contemplated by the present invention; Fig. .2 represents across-section taken through the line A-A of Fig. 1, and Fig. 3 represents a cross-section ta en. thro gh the line B--B of Fig. 1.

Fig.2 shows the tubes 2 disposed peripherally about the inner surface of the wall of reactor 1 and the four zones, namely, a, b, c and d formed by baffles 6 and 7.

Fig. 3 shows disposed in the bottom of reactor 1, heating means comprising burners 8.

There is open communication between the four zones, as shown, in Figs. 2 and 3.

Referring to Figs. 1, 2 and 3, the tubular-furnace reactor shown consists essentially of a cylindrical case 1 containing tubes 2 which, in the modification shown, are disposed in close proximity to the inner surface of the vertical wall of reactor 1. The tubes are interconnected to provide a continuous path for a flowing gasiform or vapor material.

The tubes 2 contain a hydroforming catalyst which is stationary, the individual pieces of which are preferably in the form of pills, tablets, pellets, sphere-shaped bodies or coarse granules. The pieces may be of a size or bulk corresponding to, say, an aspirin pill. As indicated, the reactor is provided with a feed inlet pipe and a product withdrawal pipe 4. With respect to tubes 2, the same need not be disposed in the manner shown and described hereinbefore. Thus, the said tubes may be disposed in any convenient position within the spaces a, b, c and (1 formed by intersecting bafiies 6 and 7 (see Fig. 2). In the interest of lower pressure drop, the said tubes may be disposed in reactor 1 in such a manner as to permit parallel flow of gasiform material and vapors through said tubes. The bafiies 6 and 7 are so disposed and arranged asto permit communication between spaces or zones a, b, c and d. At a lower point in each of zones a, b, c and d, there are burners 8 to which air and a fuel are supplied to cause the formation of hot fumes which fumes pass upwardly in reactor 1, imparting heat to the tubes 2. The fumes are withdrawn through pipe 5.

In operation, naphtha and hydrogen are fed into the reactor shown in Fig. 1 through line 3, thence passed downwardly through tubes 2 where it contacts catalyst under substantially isothermal hydroforming conditions. The naphtha and the hydrogen then pass upwardly through the riser portions of the tubes and this flow is continued until the naphtha and hydrogen pass through all ofthe tubes. Heat is supplied from burners 8 to maintain conditions necessary for hydroforming. The product is withdrawn through pipe 4.

As an alternate procedure, some of the tubes 2 may not contain catalyst and in these tubes hot gases from the burners 8 serve to heat the oil and hydrogen to maintain the oil at hydroforming temperature conditions.

In order to give a specific example of the invention, the following is set forth.

EXAMPLE I A naphtha feed having the following inspection-is treated in the above-described apparatus:

Inspection of feed Boiling range 260"-315 F. V.T. (true boiling point) Vol. percent naphthenes 47 Vol. percent parafiins 41 Vol. percent aromatics 12 Research octane number 50 Conditions in reactor 1 Catalyst composition 0.6 wt. percent platinum on eta-alumina base.

Temperatnre should be increased adu with time to counteract catalyst deactivation. gt

above, the reaction may be maintained under substan- Results. hydrogenation of 'naphthenes 'present in the "feed is very rapid, which means that the temp'eratureldrops rapidly Thelproduct obt a ellew f ei m and. therefore, the time for a trip through the firsttubes Vol-percent 8 Y n should berelatively short. fFurther down strearn towards ol-p al'omatlcs 5 5 the outlet, t he travel path of the reactants through tubes Research octane rating 926 53 containin catalyst" should be' progressively longer so It can be seen from the foregoing that unlike the adithat the slower reactions eueh'as ieemerizatiefi, ma

abatic operations, the feed need not be preheated to a temperature such as would cause thermal cracking. alt I tune to complete these 0 can further be seen that j in a compact unit described tially isothermal conditions, which is highly desirable in I P FF l rom the epirit thereefe What is claimed 1s: I

' a highly endothermic reaction such as hydroforming.-- I a example, may be any noble metalcarried on alumina,

action may vary from 850 to 9809 F. The pressure may It will be understood, of course, that the foregoing et of hydroforming naphtha the P example merely illustrates the invention without. imposing any limitation on the invention; Thus, the catalyst,- for vwhieh comprises disposing stationary shaped b s of the catalyst in a plurality of vertical tubes connected in preferably, an eta form of alumina, that is to say, 'the catalyst may be platinum, palladium, or another hydrogenation-dehydrogenation component, such as moylbdenum oxide carried on alumina. Inother words, any, of the well known hydroforrning catalysts may be em ployed. Also, the temperatures maintained in the re- I walled heatingspace, said heating space being divided into intercornmunicating compartments through each of which separately formed hot fumes .of combustion pass exment imparting heat to them, forming said fumes by burning fuel with independent control in each of ,said vary from 200 to. 800 p.s.i.g. 'With each barrel of feed c mp feedmg a stream of naphtha and y r il, 2000 t 6000 cf, of H havinga purity of 60.75%, I ftOrnvan inlet=through the interior of the tubes for conv may be fed to the reactor; It may. be also desirable to irifeed, say, 20 p.p.'m.

clude a small amount of chlorine in the platinum #or absorpficn t t m dj n h es, palladium-containing catalyst. In this same connection, T he gmgwm a and f m d it may also be desirable to include some chlorine in. the agh-tl a w y r as e P Pr uc r a m e .anoutletof-said, tubes through wh ch the product stream As usedherein, the words substantially isotherma e fWf P35 -2 .-r.'I he method; I v 7 through. the tubes containing catalyst is not greaterthan,; g a h f d ese a r e e .eemaeted with the say, 1s. 301=., but itrnay amount to a value within' e t l g ruth 9 tubes-1s Pa through a these limits. It is within the purview of this inventiom'fas e r 1 w mb 1th t 9 not contam catelystyfior previously pointed out,. to cause the hydrocarbon to be r lt sq a by e stream to compensate'for hydroformed and theh'ydr ogen to pass through tubes conheat wn a drt Wlth the t y taining catalyst, and during such passage there may be a small drop in temperature, whereupon the reactants are zation and hydrocracking shall have sufiicient 'contact 1 15 ence ofa, catalyst containinga platinum group metal" I series and arranged peripherally within a cylindrically 1 teriorally along the vertical tubes in the same compart-- tact with catalyst therein under hydroforming conditionsv c'laim 1, in which, the stream of. 'l

n 3. methodof claim; 1', further characterized in v I 40 thatthestreamof naphtha and hydrogen is given longer forced through empty tubes which; do not contain cata-ifi eontael} w h a e in Vertical fl as file S w lyst and these tubes may be positioned in one 'of the closer j p tls af P i thmllgh a lube h zones, say, zone B where hot gases from the burners ee m fia lys I H add heat to the tubes not containing catalyst -whereby The method 0 e 'ml a a' 1n he P e the reactants are reheated and thence charged to, say, enee of "5 catalyst w e 'eompnses P81591119a i f zone C where, again the hydrocarbon reactants are forced Ph ?P d 'h e reactants .l all series, through catalyst containing tubes. :ThuS, h process ofheatmgand catalystzones inside interconnectedtubes, herein proposed maintains the reactants at fairly conheatmg of Sald tubes'ln a plurality ofheatll'fg stant temperature but during preheating alway'srbelow Z n f e fuel fumes Passed thfoflgh each f fthe temperatures at which thermal cracking occurs. 'In miles wlth'mdependent Control for addlng hea'tby heat the interest'of reducingpressure drop, the hydrocarbons ng o the reactant stream passi g 'Q the to be hydroformed may be passed through the tubes in 5 tubes, and thereby lowellng a p 1n temperature O the the reactor in parallel rather thanin series. Stream of reactants undergoing reaction in Passing In a through tubes containing catalyst and a1- through a group Oftubes containing heated.

ternately, through empty tubes, that is, tubes which l onevflf Said heating snd preventing overheating do not contain catalyst, the length of the travel pathfof 0f the reactants Stream Passed through another p the reactants through the tubes containing catalyst inof tubes in another of d heating ZOIIBS- I creases progressively from the reactants inlet to the out- I A compact tabular-reactor furnace 13 let. In other words the travel path of the hydrocarbons eetel' deserlbed Whleh F PI Vertical eylmdneal to be hydroformed through the first tubescontainingcataease, F Plurahty of verfleany extetldmg Pubes adapted to vlyst may be, y, P ge ownward throug a b around contain a catalyst, said tubes being disposed in close the bend and up a second tube Thismay be d fi d proximity to the mner surface of the case, vertical interas one pass In actual operation and, f c depend secting baffle means disposed within said case and' exing on the activity of the catalyst, the preheated feed tending tfflnsvelsely l0 near the inner eflf' said entering the re'actormay initially contact catalyst during case and mtersectlng at, the central Vertical aXlS 0f four passes or through eight tubes, whereupon it would ease thus fm plurality of interqommunicating e i b reheated in, say, eight passes or through 1 empty partments, independently controlled heatingmeans disb Af reheating, h reactans may b f d posed in the'lower end of each of said compartments. through six to eight passes of catalyst containing tubes, w n i tubes d en lv i l s p rmitand after that reheated. 'This procedure of progressively ting independent control of tempeature in said compartincreasing the travel path may be followed until the dements, means for supplying'a fluid reactant to betreated "sired conversionis accomplished as indicatedby the'yield in said tubes and means for withdrawinga product octanerelationship of the product. 'It is pointed out in f di th said tubes,

lhis' connection that when the preheated feed contacts fi f a tubes in 1 thmughthe 'a 61 l (References ontollowing page) References Cited in thefilc cf this patent UNITED STATES PATENTS Winter May 8, 1923 Towne July 6, 19 37 5 Ruthruff May 30, 1939 Levine 'j Apr. 23, 1940 R ickerman et a1. July 22, 1941 Layng 'et a1. Jan. 20, 1942 Nquhafl: ..'Feb. 12, 1946 Kasel II; Ian. 20, 1953 Nyymah .I Jan. 29, 1957 

1. THE METHOD OF HYDROFORMING NAPHTHA IN THE PRESENCE OF A CATALYST CONTAINING A PLATINUM GROUP METAL WHICH COMPRISES DISPOSING STATIONARY SHAPED BODIES OF THE CATALYST IN A PLURALITY OF VERTICAL TUBES CONNECTED IN SERIES AND ARRANGED PERIPHERALLY WITHIN A CYLINDRICALLY WALLED HEATING SPACE, SAID HEATING SPACE BEING DIVIDED INTO INTERCOMMUNICATING COMPARATMENTS THROUGH EACH OF WHICH SEPARATELY FROM HOT FUMES OF COMBUSTION PASS EXTERIOLY ALONG THE VERTICAL TUBES IN THE SAME COMPARTMENT IMPARTING HEAT TO THEM, FORMING SAID FUMES BY BURNING FUEL WITH INDEPENDENT CONTROL IN EACH OF SAID COMPARTMENTS, FEEDING A STREAM OF NAPHTHA AND HYDROGEN FROM AN INLET THROUGH THE INTERIOR OF THE TUBES FOR CONTACT WITH CATALYST THEREIN UNDER HYDROFORMING CONDITIONS AND ABSORPTION OF HEAT TRANSMITTED FROM THE HOT FUMES IN THE SAME COMPARTMENT, AND WITHDRAWING HYDROFORMED NAPHTHA WITH HYDROGEN AS A REACTION PRODUCT STREAM FROM AN OUTLET OF SAID TUBES THROUGH WHICH THE PRODUCT STREAM MAKES A FINAL PASS. 